Diversity and distribution of endemic and exotic earthworms in natural and regenerating ecosystems in the Central Himalayas, India

Abstract

A comparative analysis of earthworm communities was carried out in the central Himalayas to understand the impact of deforestation and degradation of natural forest sites. Earthworm communities were studied in the climax forest, sub climax mixed forest, regenerating open grassland and 6 and 40 year-old pine forest sites with varying degree of disturbances at monthly intervals over a period of 1 year. Eight species belonging to four families were recorded from these sites, Lumbricidae (Bimostus parvus, Octolasion tyrtaeum), Octochaetidae (Octochaetona beatrix), Megascolecidae (Amynthas corticis, Eutyphoeus festivus, E. nanianus, E. waltonii) and Moniligastridae (Drawida sp.). The loss of natural climax vegetation led to the loss of endemic E. nanianus, endemic E. festivus and E. waltoni and three exotic species A. corticis, B. parvus and O. beatrix sp. and Drawida sp. appeared in the regenerating sites. Due to the process of deforestation and degradation a general decline in the density of the endemic species and the dominance by exotics were observed. The maximum number of species were recorded in 40 year-old pine forest. The present study emphasised the fact that in the central Himalayas the functional guild (endogees-anecics) change under different vegetation type; organic matter characteristics could be an important factor for this. Biological invasion was also observed in the climax forest due to the presence of exotic O. tyrtaeum. Except for A. corticis all other species had significantly higher density during the rainy season. A. corticis had maximum winter population in both 6 and 40 year-old pine forest. Population size of earthworms were significantly correlated with soil moisture, temperature and organic matter. Fire in the subclimax mixed forest caused significant decline in the population density of earthworm species. The accidental fire in the subclimax forest affected population recovery differently for different species. Thus O. tyrtaeum and E. nanianus improved significantly after 60 and 120 days after the fire.